I have a one-piece base on my standard Mauser built 404J. I was kinda compelled to go that route because the donor action had already been tapped for it. Apparently, military Mauser actions with the stripper clip port required one-piece due to screw placement. Anyway, I have had no difficulty loading this rifle when it's wearing a scope with low Warne QD rings and either of two different one-piece bases. Both bases have a cutout for loading. Warne, Leupold, and Redfield one-piece bases all have similar cutout for loading. I believe Talley also makes a one-piece base. Leupold and Redfield are proprietary for their rings. Warne QD rings are designed to clamp onto standard p-rail or old Weaver bases. In my opinion, it's a cosmetics issue. I would have liked two-piece bases but that would have required some welding and grinding to modify my receiver. I would have done it if it turned out loading was an issue. But loading is not a problem. And OP's Model 70 is CRF with "snap over" so he can always drop a round in the chamber to quickly refire his empty rifle. One-piece rail won't impede that.
Some scope/rifle combinations will require one-piece rail for proper eye relief. My Springfield 03A3 wore two-piece bases for forty years. Then I changed scopes to a Nikon 3-9x with a short tube. In order to bring the scope back for best eye relief, I had to switch to a one-piece semi-pic rail with multiple slots for rings. The rail was not expensive so figured I'd give it a try. If it didn't work out, get another scope and go back to two-piece bases. But no problems loading. It also has the cutout. But the OP has chosen a scope with no bell on the objective lens end so this will not be an issue for him. He can move his scope wherever needed in the rings for eye relief. His Model 70 should be tapped for two-piece bases (though one-piece bases made for that rifle will use same screw pattern). I don't believe their magnum rifles have integral bases machined in the receiver?